The invention pertains to a coupler for use in connecting together in a driving relationship a first member and a second member in a rotatable cutter assembly such as, for example, a roof drill bit assembly. More specifically, the invention pertains to a wet coupler for use in connecting together in a driving relationship two members in a rotatable cutter assembly such as, for example, a roof drill bit assembly, wherein these members are, for example, either two consecutive drill steels or a chuck and a drill steel.
Expansion of an underground mine such as, for example, a coal mine, requires digging a tunnel. Initially this tunnel has an unsupported roof. In order to support and stabilize the roof in an established area in an underground tunnel, bore holes are drilled in the roof. The apparatus used to drill these holes comprises a drill with a long shaft, i.e., drill steel, attached to a drill bit. U.S. Pat. No. 6,533,049 to Rein, Sr., et al. and U.S. Pat. No. 6,598,688 to Wang each show a drill steel that is useful in a roof drill bit assembly for drilling such bore holes. U.S. Pat. No. 3,554,306 to Wilburn shows a drill rod assembly that is useful for drilling roof bolt bore holes.
A roof drill bit is detachably mounted, either directly or through the use of a chuck, to the drill steel at the distal end thereof. U.S. Pat. No. 5,927,411 to Sheirer and U.S. Pat. No. 5,833,017 to Woods et al. each show a roof drill bit assembly. To commence the drilling operation, the roof drill bit is then pressed against the roof and the drilling apparatus is operated so as to drill a bore hole in the roof. The bore holes extend between two feet to greater than twenty feet into the roof. These bore holes are filled with resin and roof bolts are affixed within the bore holes. A roof support, such as roof panels, is then attached to the roof bolts.
In the past, one basic method of drilling these roof bolt bore holes has been a wet drilling method, i.e., a method where a coolant passes through the roof drill bit assembly and then impinges upon the cutting inserts and in the area of drilling through fluid passages contained in the forward and of the roof drill bit. U.S. Pat. No. 5,400,861 to Sheirer shows one example of a roof drill bit assembly that can be useful in wet drilling.
In a roof bolt hole drilling operation, it is important that the cutting inserts of the roof drill bit receive sufficient coolant, which is typically water, to maintain a sufficiently low temperature. Because drilling generates great amounts of heat, it is necessary to cool the drill bit to avoid, or at least to reduce, the thermal degradation of the cutting insert material. This is true for most cutting insert materials including without limitation polycrystalline diamond composite and cemented tungsten carbide-cobalt materials. It is thus important in a wet drilling operation for a roof drill bit assembly to deliver sufficient coolant to the cutting insert in an efficient fashion.
In the wet drilling assembly, the connections between the chuck and the roof bit along the roof drill bit assembly provide for communication between the pressurized coolant and the outside of the roof bit. During the drilling operation, it is not unusual for coolant to escape through these connections. Because the roof drill bit rotates at a high rate of revolution and the coolant is under pressure, the coolant that escapes typically does so in a high pressure stream so as to spray the operator with coolant. This makes the operator uncomfortable and makes for an unpleasant working environment. Such high pressure loss also reduces the volume of coolant which the roof drill bit assembly delivers to the cutting inserts thereby reducing the efficiency of the roof drill bit assembly.
It is therefore desirable to provide an improved wet coupler for use in connecting together in a driving relationship two members in a roof drill bit assembly wherein there is a good fluid-tight seal between the wet coupler and the driven members. By providing such a good fluid-tight seal, there is less of a chance that coolant will escape through the connections between the coupler and the driven members, and hence, more coolant will be transported to the roof drill bit.
In a wet drilling operation, it is typical that the exposed surfaces of the components suffer wear through erosion. This is the case for the exterior surface of a drill steel wherein such exterior surface suffers such erosion and wear to an extent greater than in a vacuum drilling operation. It is not unusual for a coupler to provide the connection between drills steels (or a drill steel and a chuck) whereby the exterior surface of the drill steel is useful to provide the driving connection. Because of the fact that the exterior surface the drill steel suffers more erosion and wear, the integrity of the driving connection provided by such a coupler typically diminishes along with the integrity of the exterior surface of the drill steel. A reduction in the integrity of the connection provided by the coupler reduces the efficiency of the drilling operation.
Thus, it would be desirable to provide an improved wet coupler for use in connecting together in a driving relationship two members in a roof drill bit assembly wherein the connection between the coupler and the members maintains its integrity during the drilling operation, and especially in a wet drilling operation.